RFR: 8315883: Open source several Swing JToolbar tests

[Damon Nguyen]

These are the tests being converted:

javax/swing/JToolBar/4138694/bug4138694.java
javax/swing/JToolBar/4140421/bug4140421.java
javax/swing/JToolBar/4196662/bug4196662.java
javax/swing/JToolBar/4243930/bug4243930.java

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Commit messages:
 - Initial test conversion to open

Changes: https://git.openjdk.org/jdk/pull/15748/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15748&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315883
  Stats: 209 lines in 4 files changed: 209 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15748.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15748/head:pull/15748

PR: https://git.openjdk.org/jdk/pull/15748